'Fly' in the Bible

Above him stood the seraphim: each one had six wings; with twain he covered his face, and with twain he covered his feet, and with twain he did fly.

And it shall come to pass in that day, that Jehovah will hiss for the fly that is in the uttermost part of the rivers of Egypt, and for the bee that is in the land of Assyria.

And they shall fly down upon the shoulder of the Philistines on the west; together shall they despoil the children of the east: they shall put forth their hand upon Edom and Moab; and the children of Ammon shall obey them.

Who are these that fly as a cloud, and as the doves to their windows?